Because of the human visual sensory system's enormous capacity to absorb and process information, visual displays are extremely effective in displaying a variety of information formats, such as, for example, moving sceneries, alphanumeric characters, maps, graphs, and targeting data, all of which may be superimposed on an observer's normal field of vision. Particularly, tactical military operations requiring highly complex series of tasks to be performed in unpredictable environments greatly benefit from the use of miniature visual displays, such as head-up, direct view, or helmet-mounted displays. For instance, tactical aircraft personnel are now being equipped with helmet-mounted displays (HMDs) which allow a miniature visual display system to be held on the head of the observer so as to project a display within the observer's field of vision. In the commercial sector, high-resolution HMDs can provide a "virtual reality" for entertainment and education.
In the last decade, a vast amount of effort has been expended to develop compact, lightweight visual displays, such as HMDs. Desirably, miniature visual displays should efficiently deliver an image generated from the display device, typically a cathode ray tube (CRT), to the observer's field of view with minimal or no distortion. Unfortunately, the progress made to date in the miniature visual display and, more particularly, the HMD technology has been primarily in the classical or holographic optics used in the imaging or relaying of the image. See, for example, J. R. Burley et al., "A Full-Color Wide-Field-of-View Holographic Helmet Mounted Display for Pilot/Vehicle Interface Development and Human Factors Studies," Proceedings of the SPIE, Vol. 1290, pp. 9-15 (1990).
Very little progress has, in fact, been made in developing compact, high brightness, high contrast, low power CRTs. Accordingly, the lack of suitable compact CRTs severely limited the applicability of miniature visual displays, leading to the development of miniature display systems which utilized other suitable display devices.
One such display system is disclosed in U.S. Pat. No. 5,003,330, which is incorporated herein by reference. This display system utilizes a diode array fixed within a helmet-visor structure. Although these diode arrays perform acceptably in the helmet, they have not been completely satisfactory for displaying high resolution and/or color display images. Linear diode arrays and even diode laser arrays required to achieve such improvements are either not available at the desired visible wavelengths for color display images or not available in the array sizes required for color or high resolution miniature visual display applications.
Further, prior art lasers are not suitable for two-dimensional array fabrication or micro-optic integration which is preferred for today's scanning, printing and display applications. This is due to the astigmatic beam quality of conventional semiconductor lasers as well their high divergence which make it prohibitively difficult to project high resolution images within the field of view of the observer without the use of relatively expensive and bulky optics.
Other display devices which have also been developed in an effort to replace the dominant image display device, include, for example, liquid crystal displays (LCDs), AC and DC plasma displays, thin film electro-luminescence displays, and vacuum fluorescent displays. Each of these alternative technologies, however, has fundamental shortcomings, particularly for addressing HMD applications. LCDs, for example, have a very low efficiency in generating, modulating, and transmitting light. See, for example, D. L. Jose et al., "An Avionic Grey-Scale Color Head Down Display," Proceedings of the SPIE, Vol 1289, pp 74-98 (1990). Plasma displays, on the other hand, require on the order of approximately 100 volts or more, while the other alternative display devices are difficult to scale down to sizes achievable with either the diode or laser array (approximately 20-40 .mu.m.sup.2 per element) technology necessary to achieve miniaturization.
To date, therefore, the size, nature and/or availability of wavelengths for display devices have limited the practicality and utility of miniature visual displays.
It is therefore an object of the present invention to provide a visual display system that utilizes compact, solid state, high efficient, high brightness, and high contrast display devices for providing monochrome as well as full color displays to an observer's field of view.
It is a further object of the present invention to provide a miniature visual display system that provides a high resolution color image of visual information and is suitable for a broad range of consumer, industrial, business, medical and military applications.
It is still a further object of the present invention to provide a miniature visual display system or technology that is compatible with the existing classical and holographic optics and which utilizes a display device that is superior to the prior art display devices to achieve a higher resolution.